Table 1.

Pseudosymmetry for major structural classes and for the most diversified folds

Fold class	# Folds in class	# SFs in class	% SFs with symmetry	Superfolds: most diversified fold in class	# SFs in fold	% SFs with symmetry^a
A	284	507	19%	a.24	28	57%
B	174	354	25%	b.1	28	39%
C	147	244	17%	c.1	33	36%
D	376	551	14%	d.58	59	58%
F	57	109	24%	f.13 (GPCRs)	1^b	N/A
	1038	1765	20%

Fold classes according to SCOP 1.75 (A, all alpha; B, all beta; C, alpha+beta; D, alpha-beta mixed; F, membrane proteins). Total number of folds and superfamilies (SFs) in class, with percentage of SFs deemed symmetrical. “Superfolds”, i.e. folds with the highest number of superfamilies in class, as a measure of their diversification. For each of them the percentage of superfamilies exhibiting pseudosymmetry (these results were obtained computationally using a threshold of 30%, i.e. a minimum of 30% of superfamilies associated with a given fold were found pseudosymmetric (see Ref. 1,Table S2). In that study 1831 superfamilies representing 157,432 domains were used, including Class E, not shown)

Representatives of superfamilies were used. Pseudosymmetry was detected for a number of them for each fold. With a score of 30% or more the fold is “called” as symmetric. Experience shows that other folds are symmetric but were undetected with the parameters used. An example would be the Hfq/Sm fold and others sharing an SH3 topology (b.34/b.38), which fall under that 30% threshold

We added GPCRs, classified as one fold, one superfamily in SCOP. Technically it could be classified as A: all alfa. It represents a special case of a highly diversified structural domain within a single superfamily with over 800 different GPCRs just in humans and a staggering 2300 hundred in elephants, diversifying ligand binding for a conserved signaling function within cells